1. Field of the Invention
The present invention is generally related to a support system for an outboard motor and, more particularly, to a support system that uses a plurality of elastomeric connectors, or mounts, arranged in a common plane of a finite thickness that is generally perpendicular to a driveshaft of the outboard motor.
2. Description of the Prior Art
Many different types of outboard motors are well known to those skilled in the art. All known outboard motor attach to a marine vessel in the region of the transom. Typically, a transom bracket which is attached to the outboard motor can be attached to the transom to allow the outboard motor to rotate about a vertical steering axis and trim or tilt about a horizontal tilt axis. Most support structures incorporate four or more elastomeric connectors that are used to mount the outboard motor to the transom bracket in such a way so as to isolate vibration generated by the outboard motor.
U.S. Pat. No. 5,964,197, which issued to Koishikawa et al on Oct. 12, 1999, describes an outboard motor and engine. The outboard motor body case is supported on a swivel shaft though a connecting member. The swivel shaft is vertically swingable about a tilting axis. An engine is mounted at an upper portion of the outboard motor body case with a crankshaft thereof being oriented vertically and a flywheel is mounted at a lower end of the crankshaft and disposed between an engine block and the connecting member. A dynamo is mounted within the flywheel and a starter motor is engaged with a ring gear which is formed around an outer periphery of the flywheel. Thus, since the flywheel having a large weight is mounted at the lower end of the crankshaft, the position of the center of gravity of the outboard motor is lowered. Therefore, it is possible to easily perform a tilting-up about the tilting shaft with a small force. Moreover, since the flywheel is mounted on a power taking-off side of the crankshaft, the torsional vibration of the crankshaft can be reduced.
U.S. Pat. No. 3,934,537, which issued to Hall on Jan. 27, 1976, describes a vibration isolating mount for an outboard motor. The vibration isolating arrangement for an outboard motor having a propulsion unit mounted rearwardly of the steering axis of the outboard motor includes a powerhead, a driveshaft housing having a driveshaft, and a lower unit carrying a propeller. The mounting arrangement includes an upper mount and a pair of lower mounts secured to the propulsion unit in vertically spaced relation and rearwardly of or behind the driveshaft. The top mount includes a cross bar which has a wedged-shaped cross section with the upper and lower surfaces thereof converging in the direction of propeller thrust, which is supported by a resilient bushing within a casing, and which has outer ends extending from the casing transversely to the direction of propeller thrust for connection to a swivel bracket. The lower mounts are mounted in laterally spaced recesses provided in the driveshaft housing. Each of the lower mounting units includes an insert which has a wedge-shaped cross section with the upper and lower surfaces thereof diverging in the direction of forward propeller thrust and which is supported by a pair of resilient pads disposed between a pair of spacer members which fit snugly into opposed grooves provided in each drive shaft housing recess.
U.S. Pat. No. 4,384,856, which issued to Hall et al on May 24, 1983, describes a lateral support arrangement for an outboard motor with separate tilt and trim axes. The outboard motor comprises a transom bracket adapted to be connected to a boat transom, a propulsion unit which is mounted to the transom bracket for pivotal steering movement of the propulsion unit in a horizontal plane and for pivotal movement of the propulsion unit in a vertical plane between a lowermost running position and a full tilt position, in which the propulsion unit includes a first pivot connecting an intermediate bracket to the transom bracket for pivotal movement of the intermediate bracket relative to the transom bracket about a first pivot axis which is horizontal when the transom bracket is boat mounted, whereby movement of the propulsion unit through a tilt range is enabled. A second pivot connects a swivel bracket to the intermediate bracket for pivotal movement of the swivel bracket with the intermediate bracket and relative to the intermediate bracket about a second pivot axis parallel to the first pivot axis, whereby movement of the propulsion unit through a trim range is enabled. A king pin pivotally connecting the propulsion unit to the swivel bracket for steering movement for steering movement of the propulsion unit relative to the steering bracket about a generally vertical axis and for common pivotal movement with the swivel bracket in a vertical plane about the first and second horizontal axis is provided along with hydraulic cylinders for sequentially displacing the propulsion unit from the lowermost position through the trim range and then through the tilt range to the full tilt position. A support is provided on the transom bracket for providing side support to the intermediate bracket.
U.S. Pat. No. 4,395,238, which issued to Payne on Jul. 26, 1983, describes an outboard motor mounting means affording upward tilting without travel of the motor forward of the boat transom. The marine propulsion device comprises a bracket adapted to be fixed to the transom of a boat and including a generally planar mounting surface engaged with the boat transom when the bracket is boat mounted. The bracket also includes a lower part having a lower bearing with a steering axis which extends generally vertical when the bracket is boat mounted. A member includes a lower portion extending in the lower bearing and a pair of laterally spaced arms connected to the lower portion and respectively including upper horizontal bearings having a common axis located in spaced relation above the lower bearing. It also comprises a steering arm fixed to the member for steerably rotating the member within the lower bearing about the generally vertical axis. The propulsion unit includes a powerhead and a lower unit extending fixedly downwardly from the powerhead and including a rotatably mounted propeller. Trunions on the powerhead adjacent to the top thereof and received in the upper horizontal bearings for pivotally connecting the propulsion unit to the member for movement about the horizontal axis between a running position with the propeller submerged in water and with the propulsion unit located wholly aft of the bracket mounting surface are disclosed. An elevated position with the propeller substantially out of the water and with the propulsion unit located wholly aft of the bracket mounting surface is also described
U.S. Pat. No. 4,545,770, which issued to Ferguson on Oct. 8, 1985, described an outboard motor mounting arrangement. A marine propulsion installation comprises a marine propulsion device which includes a transom bracket having a mounting portion fixed to the rear of a boat transom below the upper edge thereof. It also includes a pair of laterally spaced arms extending upwardly from the mounting portion and including respective upper ends located rearwardly of the boat transom and above the upper edge thereof. A swivel bracket comprises a mounting portion and a pair of laterally spaced arms extending upwardly from the swivel bracket mounting portion and including respective upper ends. It also includes a tilt pin connecting the upper ends of the transom bracket and swivel bracket arms to provide for pivotal movement of the swivel bracket relative to the transom bracket upon the tilt axis which is horizontally located rearwardly of the transom and above the upper edge thereof. A propulsion unit includes an internal combustion engine and a propeller mounted for rotation and driven by the engine along with a king pin which connects the propulsion unit to the swivel bracket mounting portion for pivotal steering movement of the propulsion unit relative to the swivel bracket about a second axis transverse to the tilt axis.
U.S. Pat. No. 4,979,918, which issued to Breckenfeld et al on Dec. 25, 1990, describes an outboard motor vibration isolation system. The marine propulsion device comprises a propulsion unit including a cavity defined in part by a wall. It also comprises an opening communicating with the cavity and a rubber mount insertable into the cavity through the opening. Furthermore, it comprises an expandable wedge insertable through the opening and into the cavity. The wedge is securable to the propulsion unit and engageable with the rubber mount for fixedly securing the rubber mount to the propulsion unit and between the insertable expandible wedge and the wall of the cavity.
U.S. Pat. No. 5,083,949, which issued to Breckenfeld et al on Jan. 28, 1992, describes a marine propulsion device with a resilient mounting for a propulsion unit. The marine propulsion device comprises an internal combustion engine including an engine block, a driveshaft housing, a propeller shaft rotatably supported by the driveshaft housing, and adapted to support a propeller. It also comprises a driveshaft extending through the driveshaft housing and including an upper end driven by the engine and a lower end drivingly connected to the propeller shaft. A resilient mount is connected solely to the engine block and adapted to be supported by a kingpin.
U.S. Pat. No. 5,192,235, which issued to Dunham et al on Mar. 9, 1993, describes an outboard motor vibration isolation system including an improved rubber mount. A marine propulsion device comprises a propulsion unit including a wall defining a cavity, and a rubber mount which is located in the cavity and which includes an annular outer shell. The shell has an outer surface engaging the wall and an inner surface defining an axially extending bore having a minimum diameter, and it is adapted to be connected to a kingpin. It also includes an end core portion having a diameter less than the minimum diameter and an opposite end core portion having a diameter greater than the minimum diameter and a resilient member extending between the outer shell surface and the inner core.
U.S. Pat. No. 5,443,406, which issued to Mondek et al on Aug. 22, 1995, describes a vibration isolating mounting for an outboard motor. A marine propulsion device comprises a propulsion unit assembly having forwardly located laterally spaced portions respectively including laterally aligned outwardly opening sockets and laterally aligned horizontally extending apertures communicating with the sockets. A kingpin assembly includes a portion located between the laterally extending portions and including a laterally extending bore aligned with the apertures and rubber mount assemblies respectively engaged in the sockets and having respective bores in alignment with the bore in the kingpin assembly. It also includes a laterally extending bolt projecting through the bores and through the apertures in spaced relation thereto and including a head engaging one of the rubber mount assemblies and a nut threaded on the bolt and engaging the other of the rubber mount assemblies.
U.S. Pat. No. 5,460,552, which issued to Blanchard et al on Oct. 24, 1995, describes an adapter plate mounting system for a marine jet propulsion unit. A mounting system for connecting a marine power head having a vertically disposed crankshaft to a jet propulsion unit is disclosed. Its purpose is for isolating operational vibrations including an adapter plate, a power head mounting apparatus on the adapter plate for securing the power head to the plate, and a connecting assembly for connecting the adapter plate to the jet propulsion unit at at least one point. The connecting assembly includes resilient portion to isolate vibrations generated by the power head.
U.S. Pat. No. 5,511,997, which issued to Yoshida on Apr. 30, 1996, describes a mounting arrangement for an outboard motor. The improved mounting arrangement for an outboard motor on the transom of an associated watercraft embodies elastic mounts comprised of an inner tube, an outer tube, and an interposed elastic member. The inner tube defines a cavity that receives the elastic member that is non-circular in cross section so as to permit a greater volume of damping material in a given spatial relationship.
U.S. Pat. No. 5,846,106, which issued to Kumita on Dec. 8, 1998, describes an outboard motor mounting arrangement for an outboard motor which has a body that is connected to a watercraft mounting bracket by at least one mount. The mount includes a resilient isolating member having a spring constant in a direction parallel to an axis extending from the front to the rear of the motor which is greater than its spring constant in direction parallel to a second line extending transverse to the first line. So arranged, the frequency of the excitation force applied to the isolating member over normal engine operating speeds does not correspond to the natural frequency of the isolating member in either direction and the resonant modes are avoided.
U.S. Pat. No. 6,146,220, which issued to Alby et al on Nov. 14, 2000, discloses a pedestal mount for an outboard motor. The outboard motor is mounted to a transom of a boat with the pedestal which is attached either directly to the transom or to an intermediate plate that is, in turn, attached to the transom. A motor support platform is attached to the outboard motor, and a steering mechanism is attached to both the pedestal and the motor support platform. The tilting mechanism is attached to the motor support platform and to the outboard motor. The outboard motor is rotatable about a tilting axis relative to both the pedestal and the motor support platform. The tilting mechanism is rotatable relative to the pedestal and about a steering axis. The steering axis generally vertical and stationary relative to the pedestal and is unaffected by the tilting of the outboard motor. The tilting mechanism is rotatable relative to the pedestal and about the steering axis with the outboard motor.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Those skilled in the art of outboard motor design are well aware that it has long been a goal to provide an outboard motor that runs more silently and with less vibration than preceding outboard motor designs. When an outboard motor is operating, each of its combustion chambers experiences sequential firings of the fuel/air mixture within the cylinders and each firing, initiated by a sparkplug, creates an impulse force against a piston that can be transmitted to the engine system, its support structure, and the marine vessel to which the outboard motor is attached. These impulses result in noise and vibration experienced by the operator of the marine vessel.
A properly structural support system for the outboard motor is also critically important because of its relationship to the steering stability of the marine vessel. If the support system is too xe2x80x9csoftxe2x80x9d, or compliant, steering instability can result in a dangerous condition which can significantly decrease the safe maneuverability and handling of the marine vessel. If the support system of the outboard motor is too xe2x80x9crigidxe2x80x9d, or stiff, vibration and noise emanating from the engine system are easily transmitted through the support structure to the marine vessel and the comfort of the marine vessel operator can be adversely affected.
It would therefore be significantly beneficial if a support system for an outboard motor could be developed in which vibration and noise were effectively isolated from the marine vessel while maintaining stability in the steering and handling of the marine vessel.
An outboard motor made in accordance with the preferred embodiment of the present invention comprises an engine system and a driveshaft connected in torque transmitting relation with an output shaft of the engine system. Throughout the description of the present invention, the term xe2x80x9cengine systemxe2x80x9d will be used to include an engine block, cylinder head, and other components attached rigidly to the engine. The engine system is attached to a drive shaft housing and a gearcase.
Three or more connectors are attached to the engine system proximate three engine connection locations. A support structure, or support saddle, is attached to the three connectors proximate three support structure connection locations, with the three connectors defining a plane which is within forty five degrees from being perfectly perpendicular to the driveshaft. In a particularly preferred embodiment of the present invention, the plane defined by the connectors is approximately 20 degrees from perfect perpendicularity with the driveshaft. However, this angle can be different in other embodiments. Ideally, perfect perpendicularity is desirable, but an angle of 20 degrees illustrates that deviations from perfect perpendicularity are clearly within the scope of the present invention. Throughout the description of the present invention, the relationship between the plane of the three connectors and the driveshaft of the outboard motor will be described as being xe2x80x9cgenerally perpendicularxe2x80x9d, but it should be clearly understood that a precise perpendicularity between the plane of the connectors and the central axis of the driveshaft is not a requirement. Empirical testing has shown that a range of angles from precise perpendicularity between the plane and the driveshaft are also acceptable to achieve the primary function of the present invention. A particularly preferred embodiment has a connector plane that is twenty degrees from perfect perpendicularity.
In a particularly preferred embodiment of the present invention, the support structure surrounds the engine system in the plane of the three connectors. It should be understood that although the present invention can be implemented using three connectors, a preferred embodiment of the present invention uses four connectors. The torsional resonance of the engine systems supported by the three connectors is less than or equal to 70.7% of the firing frequency of the combustion chambers of the engine system in a particularly preferred embodiment and within 65%-75% in most embodiments. Of course, it should be understood that different criteria could be used in other applications and those criteria could depend on whether the associated engine is a two cycle or four cycle engine.
A driveshaft housing is suspended from the engine system with the driveshaft being disposed at least partially with the driveshaft housing. A gear housing is attached to a lower portion of the driveshaft housing.
Each of the three connectors comprises a central shaft disposed in generally concentric relation with an outer metal tube, with the central shaft being connected to the outer metal tube by an elastomeric material. In one particularly preferred embodiment of the present invention, the three connectors define a plane which is within approximately twenty degrees from being perpendicular to the driveshaft. The support structure of the present invention is rotatably attached to a transom bracket for rotation about a generally vertically steering axis. In one embodiment of the present invention, the support structure is also rotatably attached to the transom bracket for rotation about a generally horizontal tilt or trim axis, but this rotatability is not always necessary. The driveshaft housing and the gear housing are solely supported by the support structure.
In a particularly preferred embodiment of the present invention, a center of gravity of the engine system is located aft of at least one of the three connectors, forward of at least one of the connectors, on a starboard side of at least one of the three connectors, and on a port side of at least one of the three connectors.